The cashier says something to the cook in the kitchen so they know they have to prepare your burgers (even though they are currently preparing the ones for the previous clients).

<img src="/img/async/concurrent-burgers/concurrent-burgers-03.png" class="illustration">

You pay. 💸

The cashier gives you the number of your turn.

* ✨ Add illustrations for Concurrent burgers and Parallel burgers. PR [#5277](https://github.com/tiangolo/fastapi/pull/5277) by [@tiangolo](https://github.com/tiangolo). Updated docs at: [Concurrency and Burgers](https://fastapi.tiangolo.com/async/#concurrency-and-burgers).

### Translations

	if uint64(len(bp.c)) != size {
		t.Fatalf("bytepool size invalid: got %v want %v", len(bp.c), size)
	}

	// lets drain the buf channel first before we validate invalid buffers.
	for i := uint64(0); i < size; i++ {
		bp.Get() // discard
	}

	// Try putting some invalid buffers into pool
	bp.Put(make([]byte, bp.w, bp.wcap-1)) // wrong capacity is rejected (less)
	bp.Put(make([]byte, bp.w, bp.wcap+1)) // wrong capacity is rejected (more)

   *
   * @param reader input source
   * @param charset character set used for encoding chars to bytes
   * @param bufferSize size of internal input and output buffers
   * @throws IllegalArgumentException if bufferSize is non-positive
   */
  ReaderInputStream(Reader reader, Charset charset, int bufferSize) {
    this(
        reader,
        charset
            .newEncoder()

   *
   * @param reader input source
   * @param charset character set used for encoding chars to bytes
   * @param bufferSize size of internal input and output buffers
   * @throws IllegalArgumentException if bufferSize is non-positive
   */
  ReaderInputStream(Reader reader, Charset charset, int bufferSize) {
    this(
        reader,
        charset
            .newEncoder()

	// We should always have enough capacity, but older objects may be bigger
	// we do not need stashbuffer for them.
	if globalBytePoolCap.Load().WidthCap() >= len(readers)*shardSize {
		// Fill buffers
		b = globalBytePoolCap.Load().Get()
		// Seed the buffers.
		for i := range bufs {
			bufs[i] = b[i*shardSize : (i+1)*shardSize]
		}
	}

	return &parallelReader{
		readers:       readers,
		orgReaders:    readers,

         * InterruptibleChannel and JavaLangAccess.blockedOn(Thread, Interruptible), it isn't
         * predictable what work might be done. (e.g., close a file and flush buffers to disk). To
         * protect ourselves from this, we park ourselves and tell our interrupter that we did so.
         */
        if (state == PARKED || compareAndSet(state, PARKED)) {
          // Interrupting Cow Says:

    // Starting with an 8k buffer, double the size of each successive buffer. Smaller buffers
    // quadruple in size until they reach 8k, to minimize the number of small reads for longer
    // streams. Buffers are retained in a deque so that there's no copying between buffers while
    // reading and so all of the bytes in each new allocated buffer are available for reading from
    // the stream.

	// It must keep consuming from 'in' until it returns.
	// 'in' and 'out' are independent.
	// The handler should never close out.
	// Buffers received from 'in'  can be recycled with PutByteBuffer.
	// Buffers sent on out can not be referenced once sent.
	StreamHandlerFn func(ctx context.Context, payload []byte, in <-chan []byte, out chan<- []byte) *RemoteErr

         * InterruptibleChannel and JavaLangAccess.blockedOn(Thread, Interruptible), it isn't
         * predictable what work might be done. (e.g., close a file and flush buffers to disk). To
         * protect ourselves from this, we park ourselves and tell our interrupter that we did so.
         */
        if (state == PARKED || compareAndSet(state, PARKED)) {
          // Interrupting Cow Says: